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Will26

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I was using the search feature to see how many people who had an account were ALS patients, and how many of those people fall within a certain age range. I know I've always wondered how many people who get ALS are under 30 when they get it, because I think a disproportionate amount of media coverage gets centered around early-onset cases - I think people find it more compelling to hear about someone in their 20s getting ALS than to hear about someone getting it who's lived a longer life. anyway, the problem with this is most people end up seeing ALS solely through the eyes of the media, which cause a lot of high-anxiety/hypochondriac-type people (like myself) to freak out, thinking that it's actually NOT uncommon to be diagnoses with ALS at such a young age. anyway, regarding the site: using the search feature, you can see how many people are registered under the site who have ALS - looks like around 2400 ALS patients are registered - and then you can narrow the search within the ALS community to those who are a certain age, bulbar/limb-onset, male/female, parts of the world, etc. I checked how many patients were under 30..... there were 41. 2400/41 = 58, so for every 58 people who are diagnosed with ALS, only one in those 58 will be under 30 when they're diagnosed. Does this sound right? It makes me feel a lot better, knowing the odds are so slim for getting it before 30. There are 108 members who are 30-35, meaning 1 in every 22 ALS patients will be diagnosed at that age. Apparently, Bulbar cases are clustered in the older age groups even more than ALS in general is: the number of bulbar cases is about 1/5, overall, but in the under 30 category, it's less than 1/10. My question is, does this seem like a good way to get at least a reasonable idea of what the age statistics are really like with ALS? If one's lifetime risk of getting ALS is 1/400, and only 1/58 of THOSE people happen to be under 30 when they're diagnosed, that should mean about 1/23,000 people in the general pop. are fated to get ALS before 30. Does that seem like a reasonable conclusion to make? If we accept that bulbar cases are about 3 out of every 10 ALS cases in general, that would work out to about 1/1300 lifetime risk of getting bulbar ALS, and only 4 of the 450 bulbar patients are under 30. 1/1300 people get bulbar ALS, and 1/110 of those people are under 30. That works out to a 1 in 143,000 chance of getting bulbar ALS before age 30. I realize these stats might be skewed by younger patients being more likely to use the internet as a support tool, and maybe not as many men would use it, since men are, generally-speaking, less likely to reach out for support. Anyway, am I way out in left field on this, or do you guys think this gives at least a rough idea of what the age statistics are like with ALS?
 
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The only problem with using their figures for your calculations is that not all patients are registered so the figures are not accurate. It's like saying 3 out of 5 dentists recommend Crest. We only asked 15 but 3 of 5 said Crest was better. Figures can be manipulated to say just about anything you want.

AL.
 
It's not 1 in 400 who get ALS. It's 2 in 100,000.
 
Another thing to keep in mind is that you are dealing with a sample of convenience (in this case internet gathered self-report data) as opposed to a truly representative sample. It's a common problem in statistical data gathering and analysis. As Al explained what you really have is prevalence data for registered users of patients like me who say they have ALS. There assertions are not validated by documentary evidence, although to be fair, most of the profiles I've read seem to be reasonable solid in terms of a date of diagnosed.

Further, there is bias in that many PALS may not be regular computer users, and even if they are, likely aren't to register with the specific site. Although to have a greater certainty it would have to be formally researched, I would be willing to bet that the sample bias for this database causes the exclusion older PALS.

Some of our research hounds might have some better cohort breakdowns for prevalence and incidence statistics. I imagine once you take into account the sample bias problems of the database, you'll find that even fewer under 30's are ever diagnosed with the disease than your calculations based on the database. I think the message to yourself is sound, ALS in under 30's is very rare, but you might have cause for an even rosier outlook ;)

Take care,

Robert

PS My favorite advise on avoiding repsonse bias from grad school was the following: Always ask birth control questions before asking religious preference.
 
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That's what I was thinking Robert....those numbers looked small, thus increasing the percentage falsely....

I also think that if you had accurate numbers...your percentage would be much smaller giving you a greater feeling of peace
 
The other thing about statistics and probabilities is that they really don't mean much until you are one.

Dang I'm being a butt today. Wonder if I should add emotional lability to my list?

Nah.
 
According to CDC mortality data the chance of dying from ALS in the 25 - 34 age bracket is 1 in 1,487,617. That's from data collected from 1999 - 2005. So I'd say you're in left field :)
 
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